Adjustable bladed impeller



Sept. 27, 1955 J. THEVENAZ 2,719,000

ADJUSTABLE BLADED IMPELLER Filed May 22, 1952 Q Fig.2

M VENTOR N 729E VENA 2 F BY United States Patent Ofiice 2,719,000iatented Sept. 27, 1955 ADJUSTABLE BLADED IMPELLER Jean Thevenaz, LesTuileries de Grandson, Switzerland, assignor to Paillard S. A.,Sainte-Croix, Switzerland, a corporation of Switzerland Application May22, 1952, Serial No. 289,308

Claims priority, application Switzerland May 29, 1951 3 Claims. (Cl.230-114) Some apparatus require considerable ventilation for difierentspeeds of rotation of the fan. This is particularly the case inconnection with cinematograph projectors provided with a single motorfor driving the film and for ventilation and adapted to operate atdifferent speeds, for example when the apparatus is provided for silentfilms or sound films, of which the speeds are respectively 16 and 24images per second. Fans of the normal type have serious disadvantages asthey must be dimensioned to provide sufiicient ventilation at low speedsand absorb at high speeds, a force which is often inadmissible whilstproviding a uselessly exaggerated ventilation.

The present invention has for its subject a fan, particularly for acinematograph projector, which tends to remedy the above mentioneddisadvantage, by the fact that it comprises a device for adjusting thesupply of air, said device being so controlled as to ensure nearly thesame supply of air at least at two different speeds of rotation of thefan.

One form of construction of the subject of the invention is shown, byway of example, in the accompanying drawings, wherein:

Fig. 1 is a view parallel to the plane of rotation of a fan according tothe invention, with parts partly broken away.

Fig. 2 is a section on the line IIII of Fig. 1.

Figure 3 is a perspective view of one fan blade and its associatedspring assembled in accordance with the invention.

A plate 1 is secured to a sleeve 2 adapted to be secured to the shaft ofa motor for driving the fan. An annular part 3 is secured parallel tothe plate 1 by means of screws 4 and distance pieces 5. The blades ofthe fan are formed by plates 6 having a stamped portion 7 in the form ofa semi-cylinder, of which the ends project from the edges of the saidplates and form the pivots 8 of the blades. The pivots engage with theholes 9 provided in the part 3 and the plate 1. The plate 1 has arcuateslots 10 in each of which is located a projection 14 of the blades 6,which results in limiting the possible rotation of the said blades. Thelatter are subjected to the action of springs 11, each formed by a bentrod of which one end is curved and located in a hole 12 of the plate 1,the other end bearing against the blade 6. The rod is held at anintermediate point by a lug 13.

The center of gravity of the blades is located between the archedportion 7 and the end opposite to that against which the spring 11bears.

When the fan is not driven in rotation, the blades are subjected to thesole action of springs 11, and occupy the position shown in Fig. l, inconnection with blade 6a.

When the fan is driven in rotation, centrifugal force acting of thespring 11. When the speed exceeds a predetermined limit, the action ofcentrifugal force is greater than that of the spring and the bladepivots and takes up the position of the blade 6b, shown in Fig. 1. Inthis position, which is determined by the length of the slot 10, theblade displaces a smaller quantity of air than in position 6a.

The two extreme positions of the blades 6 are so determined that thedelivery of the fan is the same for at least two different speeds ofrotation of the fan. By judicious selection of the constancy of thespring and of the eccentricity of the center of gravity relatively tothe pivotal axis of the blade, it is possible to obtain a nearlyconstant delivery of the fan for all speeds of rotation included betweentwo limit speeds.

Such a fan, applied to a cinematograph projector, enables a correctventilation to be obtained both during projection of silent films at aspeed of 16 images per second and of Sound films at a speed of 24 imagesper second. This fan enables the avoidance either of the addition of anauxiliary motor of constant speed only driving the fan, or the selectionof a single motor of high power, extremely heavy and expensive. Further,a uselessly accentuated noise of ventilation is also avoided during theprojection of sound films.

I claim:

1. A radial fan comprising blades mounted in a pivotal manner between aplate and an annular part, a number of springs equal to that of saidblades, each spring cooperating with a blade, each of said springs beingformed by a bent rod, one end of said rod being bent and located in ahole of said plate, the other end of said rod bearing against an edge ofsaid blade, the center of gravity of said blade being located oppositeto said edge with regard to the axis of rotation of said blade, so thatthe action of centrifugal force acting on said blades is opposed to theaction of said springs, thus ensuring a nearly constant delivery of airfor different speeds or rotation of said fan.

2. A fan according to claim 1, wherein each of said blades has a stampedpart in the form of a semi-cylinder of which the ends project from theedges of the blades and constitute their pivots of rotation.

3. A fan comprising a plate, an annulus, means spacing said annulusabove said plate, a plurality of blades interposed between said plateand annulus and pivotally mounted thereon, each of said blades having adepending extension, said plate having a plurality of apertures, each ofsaid plates having its extension positioned in a respective one of saidapertures, a plurality of springs, each of said springs being a rod, oneportion of said rod being secured to said plate, another portion of saidrod engaging a blade at a distance from the pivotal axis of said blade,said pivotal axis being located between the center of gravity of saidblade and the point of engagement of said rod with said blade, wherebywhen the fan is rotating the centrifugal force acting on each of saidblades is opposed by a spring so that at different rotative speeds theblades assume diiferent positions.

References Cited in the file of this patent UNITED STATES PATENTS2,253,406 Wagner Aug. 19, 1941 2,351,516 Jandasek June 13, 1944 FOREIGNPATENTS 280,189 Germany Nov. 7, 1913

